JPH06261720A - Device for sterilizing carton - Google Patents

Abstract

PURPOSE: To sterilize the inside of a previously formed carton before packing by installing a tube-like ultraviolet lamp over a conveyer for carrying cartons and cooling a slender half parabolic reflector. CONSTITUTION: Cartons 2 are carried on the conveyer 4 mutually at regular intervals to passes under an ultraviolet lamp assembly 6, packed by a packing mechanism 8 and closed by a closing and sealing station 10 to be heat-sealed. The ultraviolet lamp is the mercury lamp like a tube and of a middle-level pressure and is at least partially surrounded by the slender half parabolic reflector. The reflector is cooled by cooling air, etc., to optimize light from the lamp.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a method and apparatus for filling and sealing cartons with food, and more particularly,
A method and apparatus for sterilizing the interior of a carton prior to filling.

[0002]

BACKGROUND OF THE INVENTION Milk and juice are typically packaged in cartons that are sterilized under refrigeration to prolong the shelf life of their contents. When milk or juice is packaged in sterile packaging, the contents can be stored at room temperature for a significant amount of time without damage. Both of these packaging processes require effective sterilization of the carton interior prior to filling. Sterile packages containing milk or juice can be stored at room temperature for a significant amount of time. This is because the bacteria that normally cause damage are killed during the packaging process. Various methods and devices have been developed for aseptically filling milk and juice. For example, US Pat.
No. 5,145, discloses an aseptic packaging machine with a conveyor, in which a preformed carton advances on the conveyor under an ultraviolet germicidal lamp to expose the contents of the carton to ultraviolet radiation. Furthermore, before passing under the UV lamp,
A germicidal solution such as hydrogen peroxide may be sprayed inside the carton. The use of high intensity lamps requires the provision of a shutter device for safety or to prevent overheating of the carton. During normal operation, the UV lamp is housed within the filling machine to prevent exposure of the operator to UV light. If the filling machine is stuck or for some reason the operator has to open the door of the filling machine, a mechanism to minimize UV exposure should be provided. Ultraviolet light can be turned off or blocked. Extinguishing the ultraviolet light requires a long starting time, but blocking the ultraviolet light protects the operator and eliminates the time loss at startup.

US Pat. No. 4,289,728 discloses a method for sterilizing surfaces such as food containers by adding a solution of hydrogen peroxide and then radiating ultraviolet light. This patent has a peak UV intensity of 25
It shows that it occurs at a wavelength of 4 nm. The concentration of the hydrogen peroxide solution is not more than 10 weight percent and the hydrogen peroxide solution is heated during or subsequent to the radiation. Modern carton technology with UV sterilization is limited by the low intensity of UV lamps that can be used.
Ultraviolet power of 0.1-1 W / cm ² was previously considered a high intensity source for sterilizing packaging (Morndel,
1977). Low power lamps of 0.1-1 W / cm ²
It can be cooled by convection and is effective in sterilizing flat surfaces in close proximity to the lamp. Recent developments in the area of medium-pressure, high-power mercury UV lamps have increased light output to 50-250 watts (1) per inch of bulb length.
7-85 watts / cm ² ). This type of lamp has a long cylindrical quartz glass tube containing medium pressure mercury and having electrodes on both ends. Due to the high power consumption of these lamps, it is necessary to utilize a cooling device to prevent overheating of the lamp and to allow a restart after a temporary lamp shutdown.
The cooling device generally consists of a quartz sleeve surrounding the lamp, through which air or water circulates.

While UV sterilization is suitable for sterilizing flat films, it is limited in its application to preformed angled containers due to the geometric and physical constraints associated with UV light. Has been regarded as something (Morndel, 19
1977). If a simple UV lamp is placed in close proximity above a preformed container, such as a gable top carton, the effectiveness of sterilization is severely limited for several reasons. The total luminous flux entering the carton is the carton opening (55 x 55 mm, 7 for a typical gable top carton).
Limited to light directed through 0x70mm, 95x95mm). The light emitted from the ultraviolet lamp decreases in luminous intensity as the square of the distance from the light source. Thus, as the carton depth increases, the luminous intensity decreases significantly.
Another issue when sterilizing cartons with UV light is:
The light enters the top of the carton and radiates towards the bottom, which is substantially parallel to the sides of the carton. The sterilizing effect of the light hitting the side surface is extremely small because the incident angle is small. Thus, the sides of the carton are the most difficult to sterilize, especially in the case of tall cartons. 2 of the carton when the carton is positioned on the conveyor
One side lies in a plane parallel to the lamp axis, and the other two sides intersect the lamp axis. Due to the elongated lamp, the radiation strikes the lateral sides of the carton at an angle of incidence greater than the angle of incidence of the parallel sides of the carton. When a single UV lamp is installed above the center of a 70 × 70 × 250 mm rectangular carton, the effective luminous intensity at the bottom of the carton is reduced to 13.0% of the maximum luminous intensity at the distance from the source. . The sides of the carton, transverse to the lamp axis, receive light from the entire length of the bulb. The light emanating from the side lamp reflectors facing the parallel carton has the maximum angle of incidence and thus has a luminous intensity equal to 27 percent of the luminous intensity of the lamp.

A typical configuration of a cylindrical UV light device is:
It has a single mirrored lamp in a water-cooled sleeve placed in a reflective housing with a shutter. This configuration is suitable for sterilization of flat surfaces and shallow cartons, but it is not suitable for sterilization of tall cartons because the light intensity decreases sharply with increasing distance from the bulb. While conventional methods and equipment provide satisfactory results for flat films, they are not effective in sterilizing preformed cartons.

[0006]

SUMMARY OF THE INVENTION The present invention is to substantially improve the efficiency of a device for sterilizing the interior of a preformed carton prior to filling.

[0007]

This object is achieved in accordance with a preferred embodiment of the present invention by utilizing an ultraviolet lamp cooled in the cooling surface of the elongated semi-parabolic reflector by radiation of heat. The shape of the semi-parabolic reflector and the position of the UV lamp with respect to the focal points of the two parts of the parabolic reflector provide much more UV radiation to the bottom of the carton than is obtainable by conventional methods and devices. The position of the UV lamp with respect to the reflector and the cooling airflow behind the reflector control the operating temperature of the lamp and a more effective surface sterilization is achieved. An important feature of the invention is the use of two semi-parabolic reflectors that direct the UV light to the sides of the carton. Positioning the UV arc of the lamp at the focal point of the semi-parabolic reflector provides a UV light with a large angle of incidence on the sides of the carton and a high UV intensity on the sides and bottom of the carton. Since the heat is accumulated due to the UV lamp, the lamp
Radiation cooled using an aluminum reflector. Air is circulated to cool the back of the reflector to maintain a uniform reflector temperature and lamp temperature. The aluminum surface effectively reflects light of germicidal wavelengths and effectively absorbs sufficient radiant heat to cool the lamp. The cooling device provides a heat sink that maintains the temperature of the lamp substantially constant. Maintaining a constant lamp temperature is necessary to maximize the UV light output, which minimizes restart time after a production interruption and extends lamp life.

Water-cooled shutters are used to limit the ultraviolet light from the lamp assembly when the conveyor is stuck or when the operator opens the door of the filling mechanism. Shutters are required for safety reasons, where the operator is not exposed to UV light and prevents overheating of the carton that has stopped just below the lamp. Although blocking the light increases the amount of heat, it must be removed by a cooling device to prevent overheating of the lamp. Excess heat is removed by air cooling and water cooling of the shutter. For longer shutdowns, the lamp power is halved to minimize temperature rise. Setting the lamp power at half allows light to be generated without the need for long start-up times.

[0009]

EXAMPLE A common form of container for milk and juice is
Known as a gable top container. The container has a paperboard support with a plastic coating on the inside and outside so that the top of the carton can be gabled and sealed. Referring to FIG. 1, the carton 2 typically has a heat-sealed rectangular bottom, which is placed on a conveyor 4 that advances stepwise to the right as viewed in FIG. . The cartons 2 are placed equidistant from each other and the cartons advance in two positions during the stepwise advancement of the conveyor. During each stepwise advance of the conveyor,
The carton is immobile for processing. The carton first passes under the UV lamp, exposing the inner sides and bottom of the carton 2 to UV light. At the next station, the carton is filled by the filling mechanism 8. The carton then passes through a closure and sealing station 10, where the carton is closed. Heat is applied around the top of the carton, which then passes between the clamping jaws that heat seal the top. The sealed carton is then carried on the conveyor 4.

The UV lamp is preferably a medium pressure mercury lamp. The lamp body is in the form of a quartz tube. The electrodes are sealed in glass at each end of the tube. The tube is filled with an inert gas such as argon. A small amount of mercury is in the tube. The medium pressure operating pressure is preferably 100 to 10,000 torr. The lamp operates from 1100 to 1500 degrees Fahrenheit (593 to 816 degrees Celsius). When a high potential is applied between the electrodes, all of the mercury evaporates and an arc is generated between the electrodes, resulting in UV radiation with a wavelength of 220 nm and above (preferably 240-370 nm). By limiting the emission from the lamp to wavelengths above 220 nm, ozone formation is avoided. Suitable lamps for use in the device of the present invention are commercially available from Aquinix, Inc., Ellanger, Kentucky, USA. The lamp assembly 6 has a housing 12 in which an ultraviolet lamp is mounted (FIG. 2). The housing has an inlet tube 14 and an outlet tube 16, which are in communication with the interior of the housing 12. The air pump 18
Air is supplied to the inlet pipe 14 via the valve 20, air is made to flow into the housing 12 and air is made to flow out via the outlet pipe 16 and the exhaust valve 22. The air pump 18 preferably has a filter and a temperature controller that regulates the temperature of the air entering the inlet tube 14. A suitable power supply 24 is provided to power the UV lamp via cable 26.

Referring to FIG. 3, the housing 12 has an outer shell 28 with opposed end walls 30,32. The outlet pipe 16 is fixed to the central opening of the shell 28. An inner shell 34 with end walls 36, 38 is mounted inside the outer shell 28. The inlet pipe 14 extends through an opening in the outer shell 28 so as to directly pass air from the air pump 18 into the inner shell 34.
It is fixed to the 4th opening. The inlet tube 14 also serves as a spacer for the shell 34 that creates a suitable gap between the inner shell 34 and the outer shell 28. A plurality of rib plates 40 are attached to the inner housing 34 and each end of the housing 34. The end members 42, 44 provide a fixture for an ultraviolet lamp tube 46 extending between the two end members. As mentioned above, the lamp 46 has electrodes at each end, to these electrodes via the insulated wire 48 at each end.
Is supplied with current. Rib plate 40 and end member 4
2, 44 have a recess 50 for receiving the reflector 52. The opposite ends of the reflector 52 receive the end members 42,44. As shown in FIG. 4, the rib plate 40 extends outwardly through slots in the sides of the shell 34 so that opposite ends of the rib plate 40 engage the inner wall of the outer shell 28. The baffle plate 54 is the rib plate 40.
And fixed to the end members 42 and 44. The baffle plate 54 has a plurality of slots 56 along the center line for allowing air from the inlet tube 14 to flow into the space between the baffle plate 54 and the reflector 50.

The lower end of the shell 28 is closed by a mounting plate 58 to which a transparent quartz plate 60 is fixed. The quartz plate 60 is transparent to ultraviolet light in the range of 220 nm or more. This spectral transmission band blocks the formation of ozone by light. The mounting plate 58 has a central opening so that the radiation from the lamp can pass through the quartz plate 60 and reach the carton 2 located below the quartz plate (FIG. 3). The UV lamp 46 is mounted on the end members 42, 44 in place with respect to the reflector 52 so as to optimally focus the UV light inside the carton 2. As shown in FIG. 7, the end of the tube 46 is attached to a ceramic grommet 62 extending through a hole in the end member 42. The relationship between the reflector 52 and the ultraviolet lamp 46 is an important part of the present invention. A semi-parabolic cylindrical reflector with a light source at the focal point creates a band of light parallel to the parabolic axis. For cylindrical bulbs, the parabolic cylindrical reflector focuses the light in a band parallel to the parabolic axis. Luminous intensity decreases linearly with distance, thus
More satisfactory for sterilization at a distance from the bulb. The parabolic cylindrical reflector should be designed to place the lamp at or near the focus of the parabola in order to optimize the luminous flux. The design of such reflectors must take into account the size of the bulb, the placement of the bulb at the focal point of the parabola, and the geometrical limitations of the gable top shape carton. The shape of a parabolic cylindrical reflector is constituted by a parabola whose focal point is at the lamp. The parabolic equation is y = x ² / 4a (where a is the distance from the vertex of the parabola to the focal point). Thus, the bulb radius has a minimum dimension of a.
An ordinary medium pressure lamp with a 50 mm diameter cooling sleeve requires, at a minimum, a parabolic reflector as shown in FIG. The focal length indicates the parabolic dimension, which results in a suboptimal shape for sterilization. Because the light is parallel to the sides of the container, most of the light is not focused below the carton and the light bundle is bent by the quartz cooling sleeve acting as a lens.
In order to solve these problems, it is necessary according to the invention to reduce the focal length and to eliminate the cooling envelope surrounding the light.

As shown in FIG. 7, the reflector 52 is received in a recess 64 having a curved edge 66 on which its outer surface is seated. FIG. 8 is a schematic diagram of the relationship between the lamp, the reflector and the carton to be sterilized. The ultraviolet lamp 46 has an arc extending between the ends of the tube 46 when energized. Due to the heat generated by the arc, the center of the arc is moved vertically upward by about 3 mm with respect to the center of the tube. In FIG. 8, the center of the arc is indicated by reference numeral 68. The reflector 52 has the shape shown by the solid line in FIG. In the preferred embodiment, the distance between the apex of reflector 52 and arc 68 is 15.5 mm. The reflector 52 has a parabolic shape defined by the equation y = x ² / 4a, where a is the distance from the apex of the parabola to the focus. Reflector 5
2 actually consists of two parabolic curves with a common focus 70. The reflector 52 designated by the reference numeral 72 in FIG.
The right side of the figure shows the actual shape 74 indicated by the chain line and the central axis 7
6 and. The left side 78 of the reflector 52 has a central axis 80
It has a parabolic shape with. The actual continuation of surface 78 is shown in phantom in FIG. Therefore, the parabolic shape of the reflector 52 is a composite of two sides 72, 78, a container containing 1 quart (70 mm x 70 mm x 24
0 mm), the angle α formed by the axes 76 and 80 is 2
It is rotated 13 degrees from vertical so that it is 6 degrees. The angle of rotation of the parabolic reflector is determined by the dimensions of each carton with the maximum angle allowed by the carton geometry with respect to the lamp. The apex 70 of the reflector 52 is 2
It is shaped so that one side is a continuous curve.
When rotating the sides 72, 78, it is important that the focal points of both sides remain at the same position 68.

The characteristic of a parabola is that it strikes the surface of the parabola,
The light emitted from the focal point 68 is reflected in a direction parallel to the central axis. As can be seen in FIG. 8, the height of the carton that can be used for a particular filling machine varies depending on the volume of carton to be filled. Tall cartons, such as 1 quart, 1 liter or 0.5 gallons, have heights that make UV sterilization difficult. It is particularly important that the UV light strikes the carton sidewalls at the maximum angle allowed by the carton and reflector geometry. For a container with 1 quart (70 mm x 70 mm x 240 mm), the angle is 1 to get the optimum effect from UV light.
Should be more than 3 times. For containers with a height-width ratio of 2.0 or greater, the lamp construction of the present invention significantly improves sterilization. An important feature of the invention is the configuration of the parabolic reflector around the UV lamp tube. In a typical installation, the tubes are typically 1100 to 1500 degrees Fahrenheit (59 degrees Celsius).
To protect the tube and the reflector, operating at a temperature of 3 to 816 degrees, the UV lamp is housed in a protective quartz sleeve and a cooling medium circulating in the sleeve, such as water or air. . When the protective sleeve is removed, the amount of light captured by the parabolic reflector is increased and light scattering by the sleeve is eliminated. By removing the sleeve, the parabolic reflector can be designed to collect the maximum amount of light from the bulb by placing the focus close to the deep parabolic reflector. The deep parabola captures as much as 270 degrees of light output while directing the light to the carton area where it is most difficult to sterilize. According to the invention, the UV lamp is cooled by radiant heat transfer using an air-cooled reflector as a cooling element at 75 degrees Celsius. Moreover, when the hydrogen peroxide is in the carton, the ultraviolet light creates ionic groups of hydrogen peroxide that enhance the germicidal effect of the ultraviolet light. In the absence of hydrogen peroxide, the wavelength is 22
Ultraviolet light from 0 to 300 nm provides an effective germicidal action.

Another feature of the present invention is the use of radiant heat transfer to maintain the lamp at a suitable temperature.
Aluminum reflectors have been used to reflect ultraviolet light and absorb heat of other wavelengths to maintain proper lamp temperature. The temperature of the reflector can be controlled by controlling the amount of air passing over the reflector, which temperature is monitored by a thermocouple at the air outlet. The temperature of the reflector is kept uniform by introducing cold air just above the hottest lamp. Then
Air flows over the rest of the reflector, maintaining a uniform distribution over the surface of the reflector. Fixed temperature of housing is 5 degrees Celsius
By maintaining between 00 and 1000 degrees, the lamp can be lit continuously and overheating is avoided. In addition, sterilization is interrupted by turning off or turning off the lamp. When the lamp is extinguished, the radiant cooling evenly distributes the mercury droplets over the length of the bulb and can be easily restarted. As a result of the usual cooling with the sleeve, a mercury concentration is formed where the coolant enters the sleeve. Such a non-uniform distribution of mercury significantly delays the start-up time required to achieve sufficient UV intensity. To protect the operator, and
A shutter assembly is provided to prevent damage to the carton should the sterilization process need to be temporarily stopped. As shown in FIGS. 5 and 6, the housing 1
2 has a lateral slot 88 for receiving a shutter plate 90. The shutter plate 90 is attached so as to reciprocate by a cylinder 92 attached to the machine frame. Cylinder 9 by suitable controller
2 can be actuated to move the shutter plate 90 to the left as viewed in FIG. 6 to block radiation from the housing 12. As an additional safety device, panels 94 may be attached to both sides of the housing 12. When the shutter is closed, the heat in the housing increases and it is necessary to increase the air flow through the inlet tube 14 and the outlet tube 16 to prevent overheating of the lamp. Further, heat generation can be reduced by reducing the power of the lamp to about 1/2. This allows the lamp to operate without the need for long start-up times.

[Brief description of drawings]

FIG. 1 is a schematic view of a filling machine having an ultraviolet sterilization mechanism according to the present invention.

FIG. 2 is an end view of the ultraviolet sterilizer.

3 is a cross-sectional view of the ultraviolet sterilizer taken along line 3-3 of FIG.

4 is a cross-sectional view of the ultraviolet sterilizer taken along line 4-4 of FIG.

FIG. 5 is a partial cross-sectional plan view of the ultraviolet sterilizer.

6 is a cross-sectional view of the ultraviolet sterilizer taken along line 6-6 of FIG.

FIG. 7 is a detailed perspective view of an end member and a reflector assembly.

FIG. 8 is a schematic diagram of a lamp and reflector associated with a carton.

Front Page Continuation (72) Inventor Terence F. Manley, Minnesota, USA 55102 Saint Paul Juno Avenue 976

Claims (10)

[Claims] 1. A device for filling a carton of paperboard and for closing and sealing it, said carton being supported on a conveyor and advancing through said device, provided above the conveyor and filling the carton. In an apparatus comprising a UV lamp positioned to direct UV light inside a carton on a conveyor, an elongated housing aligned with the conveyor, a reflector provided on the housing, and at least a portion by the reflector. A tubular UV lamp, which is enclosed in a housing, and which is provided in the housing and has a parabolic shape for directing light from the lamp towards the bottom of the carton on the conveyor and for cooling the reflector. And a cooling device for optimizing the light emitted from the lamp. 2. The reflector has two parabolic sides, the vertical axis of each reflector being displaced about 13 degrees from each other, the two sides being at the center of the arc of light of the lamp. The device of claim 1 having a focal point. 3. The reflector has an inner surface exposed to the light source and an outer surface exposed to the inside of the housing made of a sheet material, and the cooling device is for cooling the fluid on the inner surface of the reflector. The device of claim 1 having a structure. 4. The device according to claim 1, wherein the reflector is made of a thin aluminum plate. 5. The tubular ultraviolet lamp is mounted in a housing with an arc of light extending along the length of the lamp and substantially parallel to the path of the conveyor in which the carton is placed. The device according to claim 1. 6. The apparatus of claim 1, 2 or 5, wherein the reflector has first and second parabolic sides joined together along the apex. 7. The housing has an outer shell and an inner shell, the outer shell having opposite end walls, the inner shell also having opposite end walls, and the reflector being the inner shell. 2. The cooling device of claim 1, wherein the cooling device is attached to the reflector and is configured to contact the reflector to provide cooling of the fluid to the inner shell and from the inner shell to the outer shell. Equipment. 8. Apparatus according to claim 7, wherein the UV lamp is a medium pressure mercury lamp. 9. The reflector has first and second parabolic reflecting surfaces each having a central axis and a focal point, the central axis of the first parabolic reflecting surface having a second parabolic reflecting surface. Intersecting at an acute angle with the central axis of the parabola, the focal point of the first parabolic reflecting surface and the focal point of the second parabolic reflecting surface coincide with the arc of light of the tubular ultraviolet lamp. The apparatus according to Item 1. 10. The device of claim 9, wherein the acute angle is about 13 degrees.